The primary objectives of this work are to examine current knowledge in the field of carcinogenesis and related fields and to identify criteria for the evaluation of carcinogenic effects of chemical and physical agents, for the evaluation of risk assessment methods, and for the prevention of cancer hazards in the human population. Laboratory methods and biological models for the detection of carcinogenic activity of chemicals are examined and evaluated, with particular emphasis on animal models of carcinogenesis and in vitro models for carcinogenesis studies. Criteria for the evaluation of carcinogenic risks from environmental and occupational human exposures are developed. Research approaches are outlined for studies in carcinogenesis mechanism addressed to the problems of occupational and environmental cancer prevention.